Chlorinative dehydrogenation of hydrocarbons

ABSTRACT

Aliphatic hydrocarbons of from four to six carbon atoms are dehydrogenated by passing the hydrocarbons and chlorine through a reaction zone containing a catalyst of calcium-nickel phosphate, promoted with a minor amount of chromia, at a temperature of from 450* to 675* C.

United States Patent Lohr, Jr. et al. June 27, 1972 [54] CHLORINATIVE DEHYDROGENATION 2,456,367 12/1948 Britton et al.... ....r252/228r2 OF HYDROCARBONS 2,456,368 12/1948 Britton etalm ....252/228.2

3,308,198 3/1967 Bajars ..260/680 [72] Inventors: Delmar Frederick Lohr, Jr., Bedford Heights; Gram Crane; Edward L. y, 3,173,962 3/1965 Carroll et a1 ..260/659 both of Akron, all Of Ohio OTHER PUBLICATIONS 1731 Assigneel The Rubber Cmmlmnlh Britton et al. 111 1nd. & Engr. Chem., Vol. 43 1951 pp. Ak1()n,0h10 I22] Filcd: Sept. 16, I970 Primary Examiner-Delbert E. Gantz [21 1 Appl' 73258 Assistant ExaminerJ. M. Nelson Related Application Data Attorney-S. M. Clark and Gordon B. Seward [63] Continuation-impart of Ser. No. 883,259, Dec. 8, 57 ABSTRACT 1969, abandoned.

Aliphatic hydrocarbons of from four to SIX carbon atoms are [52] U.S.Cl ..260/677 XA,260/683.3 y ogenated by passing the hydrocarbons and chlorine [51] Int. Cl ..C07c 11/02 gh a r ion z n containing a catalyst of calcium- [58] Field of Search ..260/677, 680 D, 683.3 ni kel phosphate, pr m d with a min r amount f hr r at a temperature of from 450 to 675 C.

[56] References Cited 6 Clalms, No Drawings UNITED STATES PATENTS 3,383,429 5/1968 Noddings ..260/669 CHLORINATIV E DEHYDROGENATION OF HYDROCARBONS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our copending application Ser. No. 883,259, filed Dec. 8, 1969, entitled Chlorinative Dehydrogenation of Hydrocarbons now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the gas-phase dehydrogenation of hydrocarbons to the corresponding olefins, diolefins, actylenes or triolefins.

In the production of unsaturated hydrocarbons, useful as polymerizable monomers in the manufacture of plastics and elastomers, a number of processes have been employed. One such process employs a suitable catalyst to convert a substantial proportion of a principally paraffinic feed to the corresponding mono-olefins, with hydrogen as a by-product. Oxidative dehydrogenation processes utilize oxygen in the feed, and yield water vapor as a by-product. The inclusion of halogen, along with oxygen, in the feed has also been disclosed.

In all of these known processes a principal aim is to obtain as high as possible conversion of the feed material, with a maximum proportion of the effluent appearing as the desired unsaturated hydrocarbons, and a minimum amount of unwanted by-products. Thus a need exists for a system which would produce a high conversion of the saturated starting materials, with a correspondingly high selectivity to olefinic or diolefinic products. Selection of the combination of a process and a catalyst system which act together to produce optimum results is of prime importance to investigators in the field of petrochemicals.

U. S. Pat. No. 2,456,367 discloses a catalyst which is essentially calcium-nickel phosphate. This catalyst is described as being effective in the dehydrogenation of olefins to the corresponding diolefins. The feed materials are restricted to olefins, however, and yields are not particularly high. Moreover, the process does not employ a co-reactant material, such as oxygen or a halogen.

SUMMARY OF THE INVENTION The process of the invention presents a means for dehydrogenating hydrocarbons with improved conversion and selectivity to the desired unsaturated hydrocarbons.

In essence, the invention is carried out by passing a mixture of the hydrocarbon feed, together with from 0.l to 2.0 moles of chlorine per mole of hydrocarbon at a temperature of from about 450 to about 675 C. and at approximately atmospheric pressure in contact with a calcium-nickel phosphate catalyst, to obtain the corresponding hydrocarbon having the same number of carbon atoms and a greater degree of unsaturation.

The hydrocarbon feed material of the invention is selected from straight chain or branched chain paraffms of from four to six carbon atoms, monoolefins or diolefins of from four to six carbon atoms, or mixtures thereof. Examples of feed materials are n-butane, n-pentane, n-hexane, isobutane, 2-methyl butane(isopentane), butene-l, cis-butene-2, trans-butene-2, 2- methyl-butene-3, 2-methyl-butene-l and mixtures thereof. Refinery by-products consisting of amixture of four-carbon compounds are a typical feed stock.

The chlorine fed into the reaction will react primarily to give HCI, and will also produce various chlorinated hydrocarbons, to a lesser degree. The reaction is designed to produce unsaturated hydrocarbons, principally, and the production of chlorinated hydrocarbons is desirably kept to a minimum. The amount of chlorine used can vary from 0.1 to 2.0 moles of chlorine per mole of hydrocarbon feed, and will preferably be from about 0.5 moles to 1.5 moles per mole of hydrocarbon. In general, higher ratios of chlorine will produce a greater degree of unsaturation in the products, but may also produce an increased amount of chlorinated hydrocarbons.

A diluent material can also be used such as nitrogen or steam, or both. Air can be used as a source of nitrogen if desired, although the process works well without the presence of oxygen. Steam is especially advantageous, as it may be easily condensed out of the product stream. From about 5 to about 35 moles of steam per mole of feed hydrocarbon can be used advantageously. The use of from 0 to about 4 moles of nitrogen per mole of hydrocarbon feed may be desirable from a handling standpoint, but is not essential to the process.

The reaction zone may be of any convenient design which gives good contact between the catalyst and the gaseous mixture passing through. Any of a number of commercial reactors may be advantageously employed.

The catalyst of the invention is essentially calcium-nickel phosphate; the characteristics and preparation of this material are described in detail in U. S. Pat. No. 2,456,367. As is indicated in the cited patent, the catalyst may advantageously be prepared in pellet form, so as to be particularly useful in fixedbed reactors.

While the cited reference states (col. 7, lines 51,52) that the catalyst is susceptible to poisoning by halogens, it was surprisingly found that its use in the process of the inventiorfivasnot impaired by the use of substantial quantities of a halogen, namely chlorine.

As a promoter, a minor amount of chromia included with the calcium-nickel phosphate has been included, giving improved results in dehydrogenation reactions such as disclosed in U. 8. Pat. No. 2,456,367.

In operation, the mixture of feed hydrocarbons, chlorine, and optionally diluent materials can be passed through a preheating manifold in which the mixture is raised to a preheat temperature of from 200 to 300 C. This step is not essential, but is helpful in that the reactants arrive at the reaction zone at a temperature close to that employed in the zone itself, and the reaction temperature can be better controlled.

The preferred temperature of the invention for the reaction zone is from about 450 C. to about 675 C., and the reactor can be jacketed to provide for heat input or removal to maintain this optimum range.

The effluent gas leaving the reaction zone is treated to separate it into its components. Water vapor is condensed out by cooling, and the unreacted chlorine and by-product HCl are recovered. The chlorine can be recycled, and the HCI can be oxidized to chlorine, which in turn can also be recycled into the reaction zone. The remaining gaseous products can be separated by fractionation if desired, or further processed in their mixed state.

The unsaturated hydrocarbon products of the invention find many uses as chemical intermediates or as polymerization monomers. By-product materials can be recycled, or recovered and used. The chlorinated hydrocarbons, while not the desired products of this invention, may also be used as polymerization monomers or chemical intermediates, with or without separating the mixture of chlorinated hydrocarbons into its components.

PREFERRED EMBODIMENTS OF THE INVENTION The following examples are presented as illustrative of preferred methods of practicing the process of the invention.

EXAMPLE I A series of trials was performed employing a heated tubular reactor, with various pelletized materials in a fixed reaction bed, as well as with an empty reactor. Analysis of the product was made with an in-line gas chromatograph. The incoming gases were preheated to 200-300 C., and the reactor was maintained at an average temperature of about 550 C. throughout the trials.

Proportions of the various incoming and effluent gases are expressed as relative gaseous hourly space velocities (GHSV), defined as the volumes of material passed through the reactor (corrected to standard temperature and pressure) per hour,

tacting a mixture of the hydrocarbons and chlorine in the ratio of from 0.1 to 2.0 moles of chlorine per mole of hydrocarbon with a catalyst of calcium-nickel phosphate promoted with a minor amount of chromia at a temperature of from 450 to 675 C.

2. The process of claim 1, wherein the atomic ratio of calcium to nickel in the catalyst is from 7.5 to 9.2 atoms of calcium per atom of nickel.

TABLE I GHSV Selectivity Chlori- C onvernatcd Run Number Butane N Cl; Steam sion Butenes BD Total cpds- Empty reactor:

1 52 178 52 l, 050 82 51 12 63 2 r i 51 178 63 1,030 89 42 15 57 29 Silica pellets:

3... 67 260 75 1, 500 74 54 23 77 8 4 72 260 140 1,690 87 31 76 12 Calcium-nickel phosphatechromia promoted:

EXAMPLE II The procedure of Example I was repeated, using a feed hydrocarbon stock which was principally Z-methyl butane 25 (isopentane). Results are summarized in Table I], showing im- 3. The process of claim 1, wherein an inert diluent is added to the mixture of chlorine and hydrocarbons.

4. The process of claim 3, wherein the inert diluent is steam, or nitrogen, or mixtures of these materials.

5. The process of claim 1, wherein the aliphatic hydrocarproved conversion and selectivity to isoprene and lsoamylenes bons consist pnmanly of butanes.

TABLE II GHSV Selectivity Percent Temp, Isopenconver- Isoam- Run Number C. tane Air N2 C1 Steam sion ylencs Isoprenc Reactor with inert support:

8 550 64 270 1,600 Trace O 0 Q 550 59 llllll 255 14 1,600 .5 55.9 7.0 C alcium-nickel phosphatechromia promoted:

10 550 58 240 ,970 Trace 0 0 565 69 275 112 470 79.0 32. 8 21. 2 600 64 292 75 220 61. 9 62. 2 21. 5 600 61 l 315 112 ,425 78. 0 39. 0 29. 8

6. The process of claim 1, wherein the aliphatic hydrocarbons consist primarily of 2-methyl butane.

i Q l 

2. The process of claim 1, wherein the atomic ratio of calcium to nickel in the catalyst is from 7.5 to 9.2 atoms of calcium per atom of nickel.
 3. The process of claim 1, wherein an inert diluent is added to the mixture of chlorine and hydrocarbons.
 4. The process of claim 3, wherein the inert diluent is steam, or nitrogen, or mixtures of these materials.
 5. The process of claim 1, wherein the aliphatic hydrocarbons consist primarily of butanes.
 6. The process of claim 1, wherein the aliphatic hydrocarbons consist primarily of 2-methyl butane. 